/*
 * (C) 2008-2012 see Authors.txt
 *
 * This file is part of MPC-HC.
 *
 * MPC-HC is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * MPC-HC is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "stdafx.h"
#include "H264Nalu.h"

void CH264Nalu::SetBuffer(const BYTE* pBuffer, size_t nSize, int nNALSize)
{
    m_pBuffer      = pBuffer;
    m_nSize        = nSize;
    m_nNALSize     = nNALSize;
    m_nCurPos      = 0;
    m_nNextRTP     = 0;

    m_nNALStartPos = 0;
    m_nNALDataPos  = 0;

    // In AnnexB, the buffer is not guaranteed to start on a NAL boundary
    if (nNALSize == 0 && nSize > 0) {
        MoveToNextAnnexBStartcode();
    }
}

bool CH264Nalu::MoveToNextAnnexBStartcode()
{
    if (m_nSize >= 4) {
        size_t nBuffEnd = m_nSize - 4;

        for (size_t i = m_nCurPos; i <= nBuffEnd; i++) {
            if ((*((DWORD*)(m_pBuffer + i)) & 0x00FFFFFF) == 0x00010000) {
                // Found next AnnexB NAL
                m_nCurPos = i;
                return true;
            }
        }
    }

    m_nCurPos = m_nSize;
    return false;
}

bool CH264Nalu::MoveToNextRTPStartcode()
{
    if (m_nNextRTP < m_nSize) {
        m_nCurPos = m_nNextRTP;
        return true;
    }

    m_nCurPos = m_nSize;
    return false;
}

bool CH264Nalu::ReadNext()
{
    if (m_nCurPos >= m_nSize) {
        return false;
    }

    if ((m_nNALSize != 0) && (m_nCurPos == m_nNextRTP)) {
        if (m_nCurPos + m_nNALSize >= m_nSize) {
            return false;
        }
        // RTP Nalu type : (XX XX) XX XX NAL..., with XX XX XX XX or XX XX equal to NAL size
        m_nNALStartPos = m_nCurPos;
        m_nNALDataPos  = m_nCurPos + m_nNALSize;

        // Read Length code from the buffer
        unsigned nTemp = 0;
        for (int i = 0; i < m_nNALSize; i++) {
            nTemp = (nTemp << 8) + m_pBuffer[m_nCurPos++];
        }

        m_nNextRTP += nTemp + m_nNALSize;
        MoveToNextRTPStartcode();
    } else {
        // Remove trailing bits
        while (m_pBuffer[m_nCurPos] == 0x00 && ((*((DWORD*)(m_pBuffer + m_nCurPos)) & 0x00FFFFFF) != 0x00010000)) {
            m_nCurPos++;
        }

        // AnnexB Nalu : 00 00 01 NAL...
        m_nNALStartPos = m_nCurPos;
        m_nCurPos     += 3;
        m_nNALDataPos  = m_nCurPos;
        MoveToNextAnnexBStartcode();
    }

    forbidden_bit     = (m_pBuffer[m_nNALDataPos] >> 7) & 1;
    nal_reference_idc = (m_pBuffer[m_nNALDataPos] >> 5) & 3;
    nal_unit_type     = (NALU_TYPE)(m_pBuffer[m_nNALDataPos] & 0x1f);

    return true;
}
